Illuminated push button switch

ABSTRACT

The electrical switch described has a push button actuator having an imperforate steel facing and a transparent backing member and fits in an aperture in a steel face plate with clearance around it. A lamp is disposed behind the backing member, light from the lamp being guided by a skirt on the backing member and escaping at shoulders on the skirt to illuminate the clearance, so as to provide a tell-tale indication on illumination of the lamp.

United States Patent 1191 11 1 3,832,506 Dewhurst Aug. 27, 1974 [54]ILLUMINATED PUSH BU'I'ION SWITCH 2,173,057 2/1365 Kat; 2618/2 S ,51 ,56451 70 D' '11 ..2 313 [75] Inventor: Alan Dewhurst, Denham, England l l aI [73] Assignee: Dewhurst & Partner Limited,

Middlesex, England Primary Examiner-Robert K. Schaefer AssistantExamznerGerald P. Tohn [22] Flled: Sept- 1973 Attorney, Agent, orFirmLawrence E. Laubscher [21] Appl. N0.: 397,725

[30] Foreign Application Priority Data 57] AB TRACT Mar. 21, 1973 GreatBritain 13691/73 June 22, 1973 Great Britain 29818/73 The electricalswitch described has a push button actuator having an imperforate steelfacing and a trans- [521 I J S. Cl. 20(1[31;4 1 1 6L1Q1g 28,240/2 5parent backing member and fits in an aperture in a [51] Int. CIT. H0lh9/16, HOlh 9718 steel face plate with clearance around it. A lamp isField of Search 159 167 168 disposed behind the backing member, lightfrom the 200/169 PB, DIG. 25, DIG. 36; 1l6/DIG. 28; lamp being guided bya skirt on the backing member 240/2 S and escaping at shoulders on theskirt to illuminate the clearance, so as to provide a tell-taleindication on il- [56] References Cited lumination of the lamp.

UNITED STATES PATENTS 2,165,199 7/1939 Batcheller 240/2 S 8 Claims, 5Drawing Figures 1 ILLUMINATED PUSH BUTTON SWITCH BAKCGROUND OF THEINVENTION This invention relates to electrical switch apparatusincluding a push button actuator which can be illuminated to provide atell-tale indication.

Such a push button actuator may comprise a metal facing member, ofstainless steel for example, and a transparent backing member, ofplastics material for example, the facing member being perforated sothat it can be illuminated by a lamp behind the backing member. Thefacing member may be perforate in the shape of an alphanumericcharacter.

Such switch apparatus is satisfactory in many environments, the facingmember protecting the backing member to a large extent. However incertain particularly hostile environments it is found that the pushbutton is still subject to damage. For example wanton damage may becaused by applying a flame to the facing member, or hammering the facingmember with a sharp object.

SUMMARY OF THE INVENTION In accordance with the present invention, thefacing member is made imperforate and a clearance is left at least partway round the facing member; the aperture has a rim on it; and thebacking member presents one or more peripheral shoulders so that a lampat the rear of the backing member can illuminate the clearance throughthe shoulder.

DESCRIPTION OF THE DRAWINGS An embodiment. of the invention will now bedescribed by way of example with reference to the accompanying drawings,in which:

FIG. 1 is a plan view of an electrical switch apparatus in accordancewith the invention but with a face plate removed; and

FIG. 2 is a sectional view on the line AA of FIG.

FIG. 3 is a side view of the switch apparatus;

FIG. 4 is a plan view of a push button member in the switch apparatus;and

FIG. 5 is a sectional view on the line BB of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT The drawings show an electricalswitch apparatus comprising a metal face plate having an aperturetherein, a rim around said aperture, a push button depressible againstspring bias, said push button comprising an imperforate metal facingmember fitting in said rim with clearance around it and a backing memberof transparent material secured to the back of said facing member andsupporting said facing member, and a source of light disposed in orbehind said backing member and behind said facing member, said backingmember presenting at least one peripheral shoulder behind said clearancewhereby said source illuminates said clearance through said margin, andsaid shoulder normally substantially abutting a complementary ledge onsaid rim to prevent ingress of foreign matter by way of the clearance.

The face plate, rim and facing member protect the light transmissivemember and remainder of the apparatus against wanton or accidentaldamage, the illuminated clearance being sufficient for indicationpurposes. Characters may be formed on the surface of the imperforatefacing member for illumination by ambient light.

The rim surrounding the aperture in the face plate is preferably ofmetal or at least has a reflective inner surface to enhance projectionof light through the clearance. For example, the rim may be chromiumplated. The rim serves also to protect the edges of both facing memberand the face plate at the clearance when the facing member is not flushwith the face plate.

The backing member preferably comprises a first peripheral shoulderadjacent the facing member and a second peripheral shoulder on anotherwise smooth surfaced skirt depending from the first shoulder. Theskirt acts as a guide for light from the source, the light escaping atboth the shoulders to illuminate the clearance. The first shoulderserves to prevent the edges of the metal facing member scraping thesides of the rim as the push button is operated and also to hinderinsertion of foreign bodies into the clearance, which might wedge thepush button.- The second shoulder normally abuts the rim, as mentionedabove, to impede the ingress of other foreign matter, such as dust andliquids.

Referring now to the drawings in more detail, the switch apparatus showncomprises a stainless steel face plate 10 (not shown in FIG. 1) havingan aperture provided with a metal rim l2 and a push button comprising astainless steel facing member 14 and a backing member 16 of transparentplastics material, which may be coloured as desired, on which the facingmember 14 is mounted. The facing member 14 fits in the aperture left bythe rim 12 with a clearance 18. A light bulb 20 mounted behind thebacking member 16 illuminates the backing member and hence the clearance18 through a margin on the backing member 16 provided by two peripheralshoulders 21 and 22 on the backing member 16. The face plate 10, rim 12and facing member 14 are all of metal, and hence are not lighttransmissive; the effect for an observer when the bulb 20 is illuminatedis of an illuminated border to the facing member 14. As shown in FIG. 2,the backing member 16 has a peripheral skirt 23 on which the shoulder 21and 22 are formed. The surfaces of the skirt 23 are smooth apart fromthe shoulders 21 and 22, so that the skirt guides the light to theshoulder 22, where it escapes.

The light bulb 20 is mounted in a housing 24 which bears on its sideselectrical switch elements 26 and 28 having plungers 30 and 32 by whichthe switch elements may be actuated. The backing member has lugs 34 and36 projecting laterally therefrom, with studs projecting from the lowersides thereof (as seen in FIG. 3) for engaging and depressing theplungers 30 and 32 on depression of the push button, to actuate theswitch elements. Compression coil springs encircling the plungers 30 and32 normally bias the push button to the position shown in FIGS. 2 and 3.

The facing member 14 has studs such as 42 (FIG. 5) secured to its rearsurface preferably by welding. During manufacture of the push button,the facing member 14 is then placed in a die and transparent plasticsmaterial injected into the die to form the backing member 16, the studssuch as 42 being embedded in enlargements such as 44 in the interior ofthe backing member 16.

The rim 12 comprises a metal die casting which is preferably chromiumplated. The die casting is partly embedded in a support of plasticsmaterial 46 which,

' again, can be formed by injection moulding. The housing 24 and supportmember 46 are secured to the back of the face plate by bolts 50 and 52which are welded to the back of the plate 10.

The support 46 also provides a channel 48 in which the skirt 23 slideswith a clearance between 0.003 inches and 0.009 inches when the buttonis centred in the rim 14.

The width of the shoulder 21 is normally 0.023 inches which prevents thefacing member 14 touching the rim Y12 and is sufficiently wide toprovide a readily visible halo on its own. The clearance between theedge of the shoulder 21 and the rim 12 is less than 0.025 inches toprevent the insertion of most common objects and in the preferredembodiment is between 0.006 inches and 0.012 inches when the button iscentred in the rim 12. The maximum clearance between the facing member14 and the rim 12 is less than 0.050 inches to prevent the insertion ofthe majority of the more robust common objects and to minimise damage byfire, the low heat conductivity of stainless steel being of advantage inthis respect. By way of comparison, the facing member 14 is just under 1inch square in the preferred embodiment.

Although the shoulders 21 and 23 are shown encircling the facing member14, and this is currently preferred at least the shoulder 21 couldextend only part way round the facing member, the clearance between thefacing member and the rim 12 being correspondingly reduced on one ormore sides.

I claim:

1. Electrical switch apparatus comprising at least one pair ofelectrical switch contacts, a push button depressible against springbias to switch said contacts, a metal face plate having an aperturetherein, a rim around said aperture, said push button comprising animperforate metal facing member fitting in said rim with clearance atleast part way round it and a backing member of light transmissivematerial secured to the back of said facing member and supporting saidfacing member, and a source of light disposed at the rear of saidbacking member and behind said facing member, said backing memberpresenting at least one peripheral shoulder behind said clearance, saidsource may illuminating said clearance through said shoulder.

2. Apparatus as claimed in claim 1 and including a ledge on said rim,said ledge being normally engaged by said shoulder to impede ingress offoreign matter by way of the clearance.

3. Apparatus as claimed in claim 2 wherein said backing member presentsa further peripheral shoulder adjacent said facing member.

4. Apparatus as claimed in claim 2 wherein said backing member presentsan otherwise smooth surfaced skirt from which said shoulder protrudes.

5. Apparatus as claimed in claim 1 wherein alphanumeric characters areformed at the front of said facing member for illumination by ambientlight.

6. Apparatus as claimed in claim 1 wherein said rim has a lightreflective internal surface at said clearance.

ing member and said face plate are of steel.

1. Electrical switch apparatus comprising at least one pair ofelectrical switch contacts, a push button depressible against springbias to switch said contacts, a metal face plate having an aperturetherein, a rim around said aperture, said push button comprising animperforate metal facing member fitting in said rim with clearance atleast part way round it and a backing member of light transmissivematerial secured to the back of said facing member and supporting saidfacing member, and a source of light disposed at the rear of saidbacking member and behind said facing member, said backing memberpresenting at least one peripheral shoulder behind said clearance, saidsource may illuminating said clearance through said shoulder. 2.Apparatus as claimed in claim 1 and including a ledge on said rim, saidledge being normally engaged by said shoulder to impede ingress offoreign matter by way of the clearance.
 3. Apparatus as claimed in claim2 wherein said backing member presents a further peripheral shoulderadjacent said facing member.
 4. Apparatus as claimed in claim 2 whereinsaid backing member presents an otherwise smooth surfaced skirt fromwhich said shoulder protrudes.
 5. Apparatus as claimed in claim 1wherein alphanumeric characters are formed at the front of said facingmember for illumination by ambient light.
 6. Apparatus as claimed inclaim 1 wherein said rim has a light reflective internal surface at saidclearance.
 7. Apparatus as claimed in claim 6 wherein said internalsurface has a light reflective metal coating.
 8. Apparatus as claimed inclaim 1 wherein said facing member and said face plate are of steel.